Communication system



Oct. 19, 1943. J. BAUMFALK COMMUNICATION SYSTEM Filed Aug. 4, i942 5 Sheets-Sheet l Mbsklo d QOH .unimo #S 2 A n /M/E/V TOR J. BAUMFALK Arron/ver 'Oct 19, 1943.` BUMFALK' 2,332,290

COMMUNICATION SYSTEM Filed Aug. 4, 1942 5 Sheets-'Sheet 2 ATTORNEY Oct. 19, 1943. J. BAUMFALK COMMUNICATION SYSTEM 5 Sheets-Sheet "5 Filed Aug. 41 194z mju uuu L T TTORA/Ey Oct. 19, 1943. J, 'BAUMFALK COMMUNICATION SYSTEM Filed Aug. 4, 1942 5 Sheets-Sheet 4 y Oct. 19, 1943.l J. BAUMFALK A 2,.'.32,290

COMMUNICATION SYSTEM Filed Aug. 4, 1942 5 Sheets-Sheet 5 lu k k t S h Q N Q Patented Oct. 19, 1943 y' UNITED 'STATES i- CoMMUuIcATIorrsv'srErr John Baum'falkj Clifton,

f Telephone Laboratories;Incorporated;A New York; N. Y., alcorporationof N ew Xork- Appucaufuigust A1, isizsgnl; No; f i 5 3 ,5m2 i l 9 Claims.

This invention relates to communication Ysystems and particularly to special service telephone systems. l

Y `he Jobject of the invention iste provide A,means to establish emergency connections tocertain preferred lines in a group sinjved by rnachine l switching means regardless ofthe busy condition of the lines themselves vor 7the busy condition near end to a given prei-erred ofgthe trunks leading tosueh Agroup of lines,

if Generally` in such community vdial exchanges there are certain levelsy or groups accessible to incoming selectors that are notused in normal service. In accordance with the present `invention such normally idle groups, reached through -a single digit operation,fare employedto-estabflish vdirect, connections to certain preferred lines,

the numberv of linesthus served beinglimited by f the number of normally unused levels or groups.` Such direct connections are then established through the contacts o f a transfer relay indi,- yviclual to the preferredlinewhich serves to sever all connection between such line and the machine switching equipment of the' community dial exchange whereby; any existing connectionfto the preferred wanted .line is summarily dismissed. g

v:`: Thus each preferred line has two'. designations,

-onefa plural digit 'designation used in regular.I

service and another 'a'r singleV digit designation used'in emergency service. I y Where all'trunks Ato the community dial exchange vare'b'usy, a Certain one of these trunks is especially equipped so that anoperator at the disf "tant end may gain access Atiieijeto virrespective of the busy condition thereof' and by use of thesingle digit' designation set up a' direct, connection from the trunk to the preferred wanted line.y Such dithe normally .used -nachine svvitchingmeans at 'the community dialiexchange feature of the inventio s a means responsive @ser sli'giivvefaib1ier'. extending weer rect connection isinuenatore of a ,by-path about Nil-LJ.; assigner.totl Bell Y nebr digitoperation'. Suchjtrunkii rovifde distantpoint with 'a' monito pointjof 'access sothatuf time permitsa announcement-"that 1s-4 invention-'providesfemergency "or Aright-'of-fcirc `W means by' en. Operate" ,may reach. one ,o f fa s mallnurn f stations assigned for"certain emergency Se Staiin l* iS *Conntedie "a line l adingthro hianauxiliary circ'uitjgeneral'- "'l' represented vby the vrectangle 2; VWhere 'theline is normallyf connected througlij the 'contacts of va may.3it01fhereg1-ar diaofcapparaius repre'- ed by therectarigle. "By the normalfr'najnipe l'llatlonjof thisapparatusy he subscriberfat station il ima'yiset upiconnetiohsgto ther Subscribers. in :thesani'eloceibr': may .extend 'his' 'linietoga, distant office over a tivo-'Way trunk' t'ogan operatorfs "oicei The" two-Way'l trunk isf represented bygthe rectangle. generis Shown as passing through an 'Qemergency controlj'circuit 6 tol'eithe'r a' tollj'orfa 'manmal o'icez" Other `trunks like that indicated ,rectangle l 5' :will 'nass pas iridifaat'edfpv the "directly'to amanuf'al oice-this being 4the 1,1'0 .elarransement-.Ih the. Same. manner 'an 4foI,)erator at" thepdistant 'manual o fce mayjextend a""connection `either over 'the' normally arranged trunks, such' as 1i o r over thderigh'tof Way frun'k s; Vpass meiuirqugh the apparatus t'v to fthe-:trank @Ownedgeinig'dem@Specialmtended f thev The incoming selector 9 4 If now the distant operator finds all the trunks, including the right-of-way trunk to the office having subscriber I busy she will seize the right.- of-way terminals of the trunk 8 whereupon'the existing connection thereto is disrupted and the operator gains control of the selector I2. By

dialing a special number, which may be-the' same as the number used to set the incming^Selector 9, the operator will set the selector I2 on to the terminal leading to relay II. Relay II is operated and in turn causes the Voperation of relays 3 and I3 sothat a connection is immediately established from the right-of-Way trunk 8, over the front contact of relays I3, II and 3 in series to the line leading to substation I.

-In this schematic drawing both a toll oice and a manual. office is indicated as the source of an emergency call tothe station I. In Fig. ithe details ofthe right-of-way trunk from the manual oflice are shown but the details of the circuit from the toll oiricer are omitted since the invention is believed to be clear throughl the explanation of the one way of carrying out the invention. With such details of. the right-of-way trunk from the manual ofiice fully explained, those skilled lin the art will be able to practice the invention when alternative terminal arrangements are required. Fig. 4 shows an outgoing trunk from a'manual office toa dial oice. This trunk is supplied with multipled talk and dial jacks I5 and I6, respectively throughout the manual switchboard, and a single appearance pair of emergency talk and dial jacks I1 and I8 respectively. An operator extending a connection to the distant dial olce will plug into jacks I5,V whereupon the sleeve relay I9 will be operated. Relayl I9 closes a circuit from ground, its armature and front contact winding of ring seating relay through vcontacts 4 and 5 of relay' 20, lower right-hand winding of repeating coil 2|, armature 5 and back contact of relay 22 to thewring of jack I5. "If the ring of the plug is properly seated. in this jack, Ya battery connection will be'found in the cord circuit which will cause the operation of relay 20. Relay 20 locks through its contact; 3 and armature 2 to resistance 23 and battery. The lower winding of relay 24 is short-circuited to signal the circuits at the distant end of the trunk,`and a circuit is` prepared for bridging the condenser 25 under control of relay 26 to operate the supervisory relay -in the cord circuit.

The dialing cord may then be inserted in the 3'I, armature 3 and back contact of relay 21 to the ring of jack I6. It may be noted that cord circuits for cooperation with jacks I5 and I6 are clearly shown and described in detail in Patent No. 2,302,587 granted on Nov. 17, 1942, to H. W. Ulrich. The incoming selector at the distant end of the trunk may now be dialed and a connectionextended through the dial office apparatus thercat to a wanted subscriber. The dialing cord is removed from jack I6 as soon as the last digit is dialed.

,v At ythe other end of this trunk the tip conductor 29 and the ring conductorA 30 connect to the circuit of Fig. 3. Upon seizure of the trunk aline relay 3 4 will respond. This in turn will operatea'relay: 35y relay 35 will operate relay 36 .andrelay 36 Willoperate the line relay 31 of the incoming selector represented by the tip, ring and sleeve'brushes 38, 39 and 40 respectively. Relay 34 also controls the code selector represented by the" Wiper 4I. The incoming selector and the code selector will both respond to the pulses of the rst digit. If the rst digit is one which representsk a normalrconnection in this dial system oice the brushes 38, 39 and 40 will be set on ya set of terminals 42 leading to the dial office equipment 43, from which a connection may be extended to a station 44, and the wiper 4I will be set on a blank terminal. then a connection-will be set up by plugging into the emergencyjacks I1 and -I 8` as will be described in detail hereinafter.` Then a special one-digit number will be dialed which will set the codeselector on a terminal individual to the wanted line. -It may be noted that the brushes of the incoming selector will also be set on terminals 45 individual to the Wanted line by this connection will be inelective dueto the operationof relays 46 and 41, since it is necessary to drop off any connection to the two-way trunk which might have been established from the dial oflice equipment over conductors 48 and 49.

It may -be noted that similar trunks which are not equipped for this emergency service may be dial jack I6, whereupon the off-normal relay 26 is operated from the sleeve of jack I6, back contact and armature 4 of relay 21, winding of relayy 26, back contact and, armature 2 of relay 28 toground. The off-normal relay 26 disconnects the'tip' and ring conductors 29 and 30 respectively from the repeating `coil 2I and gives a clear path to the tip and ring of the jack I6. The tip'conductor 29 passes through armature 2 and back contact of relay 21 to the tipy spring of jack I6 and the ring conductor 30, passes through armature I and back contact of relay villustrated by `the circuit diagram of Fig. 4 as so far described andignoring the extra equipment Vofthe emergency talk and dial jacks I1 and I8.

In this case the tip and ringA conductors 29 and 3D will lbe connected to the'ftip and ring conductors 50 and 5I respectively. In this arrangement when the central oflice end of the trunk in Fig. 4 is seized the relay 36 will'be directly controlled and this by its control ofthe line relay 31 will result in the operation of theincoming selector. Therefore when this special one-digit number is dialed the brushes 38, 39 and-40 will be set on the contact set 45 and a ypath established thereover to station 44. Since the equipment of relay 34, the code selector 4I and the relay 41v are not present in this instance the setting of the incoming selector on the terminal set 45 will be effective.

Now for purposes of illustration it will be assumed that the outgoing trunkof Fig. 4 is an ordinary circuit and isnot equipped for emergency service.V Therefore, conductors 29-and 30 are connected to conductors 50 and 5I of Fig. 2 respectively. When the trunk is seized, as described -hereinbefore a circuit may be traced from groundjthe,lower Winding of relay' 36, back-- oon- Y ductor 5I, upper rightlhand winding of repeating coil 53, armature'" and back contact of lrelay 52',

If the trunk is busy terval by.` releasing vtheir armatures.

'one Contact of V.relay 31- vertical step of the switch contacts 19 operate and close a `circuit from 'responds and=closes '-a circuit from ground;/arin`a turel andfront-contactf-of rela-y 36, back contact andarmaturel' ot relay 56, back contact" and armature 2 'ot relay 52vvinding of relay 51 Lto battery; Relay `51fres`ponds and locks" through its front contact`l and armature!! to fthe sleeve con# ducto'r'- V53 of ythe incoming 'selector on'ffwhich normalcontaots of relay 63a1r`nature" Sand front ontactof relay; ringl conductor', armature Fand-back contact-ofrelay 55, upper Winding online-relay 31 to battery. Relay"31 responds 'andY closes a circuitv from-ground, armature #and back contact of the sleeve conductorSS. r v

When vthe V'c'perator at the' distant enel-` dials relaysSG and 31 respond to'leacli open circuit in- Upon the rst release of the'armaturesof relay 35 a circuit ises'tablisne'd from groundarmature l and back Contact of relay relay 51, Winding of usloW--rel'easing relay v63 to battery, Relay 63 respondsandfholds operated over thecomplete train of` pulses'onlyj'releasing an interval after the last pulse of thetrain. The circuit 'for the energization of relay 31 during the operated'intervals ofrelay 36 may now be'traced from'v the `tip =conductor-E53, resistance Byarma'- ture and front contact of relay.;.63,armature 3` and front contact of lrelay 36 to the ringv conductorfll, so that'relayt31fis now'controlled byjthis This pointjisvbridged Vbythe resistance r(iii and condenserell for spark control. n i Uponltlie iirstrelease of the incoming selector line relay', ground isextended from thearmatureV and baclr :contactfof relayY 31,V over the'armature 2 and front contact 'of relay'54, Winding of secondI slow relay. 68, Windingv of vertical magnet @ato battery. The vertical magnet responds to each'l impulse separately and the slow'relay 68, responds to the train of impulses as a Whole.- Onthe .first the vertical off-normal ground, armature l `and lfront contact ofv relay 64, frontV contact vand armature of `vrelay 63, springs l and 2 of thel vertical off-normal con- [tracts .13, winding of.relay1lr to battery". [Relay A1l prepares circuits for the rotaryV y magnet 12 yandY the release magnet13f At the' end of the digit when 'the second slow-relay 68 releases the VArotary magnet Y12 yisenergizecl from ground, ar-

mature I and front contact of relay V34, normal contacts Aof relay 68, a-rmaturejl and 'front contact ofrelay 1|, Winding yof Erotary "magnet12 to y magnet steps the brushes on battery. The rotar to the first set of terminals'andlopens the Circuit ofrelay12.W--

- s lUpon the first energization of relay 1 I`` the ground yfrom armature hof relay G4 'is extended over the" armature'. aridib'ack contact of magnet relay 55,'armature and front contactof'line relay 31, Winding ofiiirst lslovvr relay 64 Vto battery. t Relay $4 places ground on y l 36, back contact and armature t VI of] re'lay'52, armature "3-'and front contact of 12,'- thence overY-'sprngsf4 'and 5 ofcontact set 54 V"tothe Winding of relay 55`.and in parallel therewith over the back contact and armature 3 thereof ,to the vsleeve brush 40, Since relay 955 is'shortcircuited at this time it does not operate. As the rotary magnet 12 operates` the brush 40 comes in contact with thesleeve of the first trunk of ',theselected level andas the relay 1-|l releases the rotary magnet is deenergized. When the rotary magnet closes its back contact itnow de' pends on a ground from the sleeve of the' trunk to cause the energizationof relay 1I to start another-rotary step; As Llong as grounded sleeves are encountered the relay 1l Aand the rotary magnet 12 Will control each others circuitand step the 'switch'. Anidle trunk Will have` battery'on itssleeve 'and this will cause the energization .of relayt55 which vcuts through the tip and. ring v'conductorsi55) and Si! to-.the brushes 38and 39 y'respectively and releases the line relay 31 and the instr'slow relay. .sa The relay 55 locks through the Winding 'of relay 1| andextends groundffrom the sleeve of the selectedltrunk overitsfarr'nature j 3 and-.front contact to the sleeve Wire 58.` The :regular numbers. 45

release circuit is held open duringuseof the ground'is taken voft flthe sleeve `Wire 58- and Irelay 55 releasesf'the magnet 13 isoperated andiltlie switch releases. 1` g i f j- If the dial ofce represented generallyfby'f fe rectangle 43 isV small there may be severallevels of theincoming selector Whichare not normally employed, in which case if the numbercf sta-'L tions such as" 44 is the:same-asl orless than- `the number of'suchiavailable idle levels; vthenihe arrangement ydisclosed in] FigsQlZ;` and lIima'yIv be employed, The line represented by the"` tip, ring and sleeve conductors 141,v 15 and "13 vres'peotive'ly will be connected to thezcrvst set-of contaetsfoff such /anf idle level vand may be reached' as described by dialing one digit; -Thus' there 'may be several' stations Such as; 44 each dfesignatedbyfla special one-digit number inv addition `totheir 'I he' stationy'4-4 may be lreached by dialing the incoming selector onto the'se't of terminals 42 `and then going through the regular.' dialfolfifice equipment 43. It the station'44 is busy,y how- 'A ever,l it maybeapproached by dialing thespecial one digit to set the incoming selectoronthe set of terminals 45. f

'. v'Iy'hebridgheacross the tip and lring?'including the resistance El, may now be tracedover the tip conductor 15, back contact and armature 2off relay 18","ba-ok contact an'd'armatu're Ifof relay `lliipper Windingffof relay 11'torgroundjand over the `ring conductor 14, back contact and armature [of relay 18', back Contact and armature 6- lof e relay 4E, lower Winding yof relay11 -to ground.

causes the operation of relayV 8|. This in' turn Relay 11 'responds fand'operates the sleeve rela'y 19, which `grounds the sleeve conductors 131 and -Relay 19 alsogroun'ds'conductor 83 which lc lisconnects station 44'from1the dialoiiice 'equipment 43 and establishes a-ringing circuit vfor lstation 44 which may be traced from a source of ringing current 82, armature 4 and front contact of relay 8l, back contact and armature 6 of re- {lay 83, front contact andarmature l5 'of relay 8 I,

station 44; armature I and front'contact of relay 8|,.contacts 4 and-3 controlled by armature Ivof relay 83, front contact and armature 3'of rrelay .8I, lower Winding of relay 83 to battery. If sta- .tion' 44 is idleit will be runthroughlthe lower twinding Qfjrelayf4 83hiIf; it, is busy,.and;,Wl'xen -'it answers, the increased current through the lower winding of relay 83 will cause this relay to operate and extend the talking circuit back tothe incoming selector circuit. Relay 83 locks to ground on armature-2 of relay` 8|. Talking current for station 44 is supplied through ,the,windings of relay 84. Relay 84in operating'causes the operation of relay v'18 which reverses the-tip and ringtoward the distant end andcauses the operation of the polarized relay 24 as a, Signal that the subscriber has answered. Relay 24 opens the circuit of oil-normal relay 26 and closes a bridge through resistance 85 towards the operators cord circuit to operate the usual supervisory signal therein. v

When the subscriber at station 44 hangsup relays 84 and 18 will be released and the cord circuit supervisory signal at the distant end will be operated. When the operator takes her plugl out ofk the jack I5 relay 36 will be released, resulting in the release of the incoming selector and the restoration of the connection to normal in the usual manner. When the line relay 11 and the sleeve relay 19 restore, relay y8| will be released and the line of station 44 will be'reconnected to the dial office equipment 43.

Let it now be assumed that all trunks 'from the distantend are busy and that even the trunk of Fig. 4 is busy. It may be noted that this trunk is only shown with its essential outgoing equipment, but that it also has incoming equipment and that it may as well be involved in a connection established in either direction. The operator will therefore plug into emergency jack I1. This causes the operation of sleeve relay 32 whereupon ground is extended from the'armature and front contactof relay 32, armature 4 andvback contact of relay 22, winding of slow release relay 33 to battery. Relay 33 operates relay 3 I, whereupon the ring conductor 3|) of the trunk is opened to give a disconnect signal to the incoming selector of Fig. 3 or some switch in the dial'oiflce equipment 43 leading out over conductors 48 and 49. The relay 24 if operated will be released andthe relay 28 will restore to normal to allow the off-normal relay k26 to be operated when the dialing cord is connected to jack I8. Y

Relay 3| causes the operation of relay 22 which in turn causes the operation of relay 21 and opens the circuit-for relays 33 and 3 I. Relay 33 is slow to release to allow sufficient time for the disconnect signal to the distant end. Relay-224 locks to ground supplied by the armature of relay 32. The tip and ring conductors 29 and 38 areclosed through the front contacts of relay 21 to a bridge in the dial cord circuit to bring up the line relay at the distant end of the trunk. These conductors now extend to the circuit of Fig. 3, so the tip conductor 29 may be traced through the lower right-hand winding of repeating coil 65, arma-` ture 2 and back contact of relay 86, through the right-hand winding of relay 34 to ground, and the ring conductor 30 may be traced through the upper right-hand winding of repeating coil 85,

armature I and back contact of relay 86, through the left-hand winding of relay 34 to battery. Rc-

lay 34 responds in this circuit and will follow the dial pulses from the distant end.

It will be shown that relay 34 controls thecode switch represented by wiper 4l Vand the :incorn-` ing switch representedbjyT brushes 38, 39 and 49, simultaneously. Through its armature 3,v relay 34 controls relay 36. A circuit may be traced from ground, the lower winding of relay 36, back contact and armature 4 of vrelay 52, lower right-'handvvwinding .of ,repeating coil 53, back contact and armature 4 of.relay.41,fnormal contacts of relay 81, lower left-hand winding of repeating coil 85, resistance, armature 3 and 'front contact of relay 34, upper left-hand winding orrepeating'coil A85.conductor V89, through contacts of relays 9| `and 92`to conductor 90, armatureA I and back contact of relay 41, upper right-hand winding of repeating coilV 53arrnature 3and back contact of relay 52, upper winding of relay 36 to battery. Relay 36 thus responds to the operation ofrelay 34 and will follow theV dial pulses and control the incoming switch in the mannerhereinbefore described. v

l When this circuit is seized 'at the operator o fce relay 34 operatesl as described. Relay 34 operatedy connects4 resistance 88 in vparallel with resistance 93 and relay 94 across the tip and ring looking toward relay 36 as described.l Relay 34 also operatesY relay 95 which inturn operates relays 96 andv 91. Relay 96,1operated, provides an operating path for the rotary magnet 98 of the code selector and relay 91 operated provides an operating path forthe pulse corrector relays. Relays 34, 95, 96`and 91 .are now operated.

When the operator at the distant "end dials, relay 34 will follow the dial pulses. `Relay 95 holds over pulsing and on the first pulse of each digit relay 99 operates. The path for relay 99 may be traced from battery, lwinding of relay 99, armature I and back contact of relay |00, armature 2 and .front contact of relay 91, back contact and armature I of relay 34 to ground. Re* lay 99 locks over armature I and back contact of relay |98, front contact and armature` 4 of relay 99 to ground. At the same time relay 99 operates relay |89, from its armature 5 and relay 92 from its armature 2. Relay |00 establishes a circuit from ground,rits armature 3 and front. contact, back contact and armature 4 of relay 86, winding of relay 81 to battery. Relay 92 also closesa circuit for relay 81. Relay. 81 holds the circuit of relay 36 "closed,

Relay 92 .is slow to release and hence responds to the train of pulses of the digit as avwhole, and hence" holds relay 81 operated during dialing. Relay 99 holds the connection between conductors 89 and 90 closed in place of relay 92. Relay I9!) locks under controlof the back contact of armature I-of relay 34, opens, the. locking circuit for and releases relay 99 and prepares the circuit for the operation of relaySI. Relay 99, released,

opens. the circuit for relay 92 and allows relay 92 to operate in serieswith relay I 8|) if relay 34`is still released. The loop to relay 36 is opened Y when relay SBYreleases 'and remains open only until relays 92 .and 9| release Because relays 99 and 92 are slow-releasing relays'theopen .period to relay 36 is timed toprovide adequate time for the operation of the vertical magnet 69 of the selector ,and ofthe switches beyond. i

When relay 34'reoperates relays 9|` and |00 release and prepare the circuit for the operation of relay 99 on the next pulse. lWhen the last pulse of each digit is completed and relay 34 reoperates, 'relay 81 will release,4 and when the last digit isVv `completedlwill remain released, reconnecting resistance 88 in parallel with resistance 93 and relay 94 across the trunk for supervisory purposes. v

During pulsing, ground from armature 3 and front contact of relay 99 operates the code se- `to the3windingof rotary magnet 98the oir-noreste@ Inal springs 402 are operated...The winding of .rel-ay .96 is transferred to 'thepulsing circuit but since the relay isslowft'o release it holds during pulsing. 1"O n sub equentpulses the rotary mag'- relay v96 releases. opening thev circuit'to its own winding and the winding ofthe rotary magnet 98. The code selector therefor responds only to the rst digit.

4When relay 5 6 releases itfconnects .ground 'from' thefront lContact and armature l of relay armature 2 and .bacl` contacter" relay ,.9 s; through.

If. the .code

v96 to ywiper. 4l o -'the code selector.

.selector has been stepped to aterminalto Which emergency connector is `a spec i ,c subscribers assigned, then the yf ollovving operations 'will ftake .Placa .The grund Ori viper. over conductorlpS to .cause the operation'of "reoperated; operates relays 8l Vand V41, `Vdiscornfiects lathe;

trunk from the selector banks 'and connects nit to thejfront contactsof relay 41.. Relay 41- contstheconnetcor tothe repeating .coil 85`,f r. e l leases relay 9 4, connects `relay underfc'ontrol 4| Willbe connected emergency! connector lo ffrelay Stand operates.relaylllA 4 ljelay 9411's- .leased releases relay 84 and` operates rela'y B6 ...Whichin turn` releases. relay I0 I Lf and-101; were; @batted iinl the. b... r`-use or this .trunk when seized ,through vthe emergency jacks Relays 94,: as

, atfthedistant end, Relay 11,operated.- operates .relay '1 s ,wnicn 'no1ds relay. al4 andmakes this circuit busy to selectors by placing. ground .on'the sleeve, Relay' al, operated," diseonnectsltn sublineand'icl connects theline to the transmission circuit causing'relay-84 to operate. -Relay 84 operates relay 8 6 which reverses the current to-the emergency operator as an lanswersignal and operates relayk IDI.. The. following-relays are `now -operated,'-namely,relays 34, 95, 91, 46, 41, 11, '19-,84;83,8I,86,l05 andfllll.-v Y

s Relayilllfwhih had been operated previous .tothe seizure.orthetrunk-throueh theemergenv .jacks I 1- and; f l-fremains operated as; long-as the connection tothe operator -oflioe j; trunk -i s lheld. When the operator office trunkreleases ground is; removed f-rom the s leeve- Wire |06, releasing relay |05. When relay lilo releases, groundffrorn When.

one ink Whichthe special station is located ina .smalldia'lofiice area Where 'the number of 'such .specialstations does notexceedl the number of lun- ,used levels on the incoming selector; `Ina larger areawhere there are a" smaller number offunused levels on the incoming selector and Where there .areralarger number of special stations to be served attic-digit arrangement is used. This isillustrated in Fig. 2A which may be substituted fonl'igg 2 in ther arrangement indicated inFig 5. ZAisused analternative arrangement .oigcpnnj tions' isindicated inFig. 3. In this case armaturefof relay 4 1 is connected to groundinsftea'd of t ,thefront contact ofvrelayvgfl, andthe VJfr' contact of relay 94 is connected to' 'con .duto 1.0.1 -QfFg- 2A fflhefoperation ofthe incoming selector is the "same asThereinbefore describedexcept that it v villnot reach anyspecialstation line by a "one digit'ope tionas before.; When a special line gifs wanteditjyvillbe driven to anunused level and Ithen' restored to 'normal While theA code selector Iof Fig. 2A'malres 'the selectiono 'the'partic'ular yvanted vs 1: e cial' station..

.' Let it be assumed that station |68 is designated for ernergencyf'calling by the number in addi- .tion toits regularnumber in the dial odceequipv dmehr rme: f This @neun may be `seized at the yoperator;'oiiice either when it is lfree or when it "is-busy. 'thetrunk is busythen i'tmust be ,seized ovefthe emergency jacks l1 and i8.` When it is freeitmay'jbe seized overthe'regular jacks asfwell astlie. emergency jacks. If the circuit is mbusy'jthen "as herelnbefore described -a disconnect signal 'Willbe' given.'4 which Will return the incorn- .ing selectorto itsnormal position and thencause thejoperatioirof theline relay H0." The line 'relay l l il.jiri operating. will cause the` operation 'inbefore described.

hen theoperator dials relay H0 follows the v'd; ial p u,ls desired terminal'.

relay I i3. releases.v :Relay 'o n. jperating oircuit s, Kb) opens' the" vcircuits tothe 1 otajtry n'iagn'ety H4, and (c) connects ground .fromarrnature I and: frontV contactjof 1 el2 i y` f l`l lV over the baci; contact` and 'l armature 'wiper l I of the code selec'- not the rst digitofa Arme end of thenrst'digit l' l released (a) opens tor. 'If theflrstjdigit is *right-Ofway numbentne code selector will have stelJDd'j10j ajterrninall to which Yrelay H6 is not connectedfand therefore when relay H3 releases the-front vcontact andarmature l o'ffrelayl'l is wise affect ther onnection. When the emergency yoperator disconnects opera'ted 'relaysand the code selector to lrestoringthe circuit'to normal. l`

release i1 arrangement hereinbefore `cvlescribe'-clivvas relay `34 releases causing all at tneend of the' rst digit'it does not reoperate fand the s 'bse'quent'digits do not affect the code `switch.. '1 `ne.code' switch ,now remainsfin 'that `'position url tiljthe call should the rst digit correspond to the rst digit of a right-of-vvay number, 11 as we have assumed, ich?. ,09de 'Switch will have been stepped to a .terminal'to which' relay H6 is connected and vhen relay H3v releases `at the end of the' first .di'git'f'relay- H6 operates. This lcircuit ma'ybe traced from groundarmature l vand front con- ,tact orelay.. .I l l, armature 2 and back contact of. relay l'lj3,'wi per l l5 no'W resting on its 1tli-cor'1- tact, armature 5 and back contactl of relay H1, windngof'rel'ay H6 to battery.A Relay H6 'operatedilocks 'under control of relay l i3 and 'operates "relay 11.12,. Relay H1 operated (a) locks under Lco'ntrol of relay Ill', (l2) operates y'relay 41, c) opensthe operating circuit of relay H6 and (d) :operates the release magnet H8, restoring the 'e selector to normal. When the code selector Aire ches'normal relayv H3 vagain operatesthrou'gh .c ausingthecodeselector'to ste'p to the `theofl-normal contacts I I 9 in their normal posisubscriber.

vfrom relay |24.

tionand the circuit to the release magnet is opened. Relay H3 operated, releases the relay H5 and provides a path for steppingV the code switch as on the rst digit. Relay H6 released provides a path for operating relay |20 when relay,y I|3 releases at the end of-.the second digit. At the end of the second digit relay H3 will .release in the manner hereinbefore described. Relay H3 released, (a) opens` its own' operating circuit, (b) opens the circuit tolthe rotary magnet II 4 and (c) connects ground from lrelay I throughcontacts on the relaysII and II1 to Vthe wiper |2| lto operate relay |20. This circuit may be traced from ground, armature I and front contact of relay III, armature Zandback Vcontact of relay H3, armature and. back contact of `rela-y H5, front contact and armature 4 of relay I I1, brush |2| now on its 1th contact, winding 'of relay |20 to battery and ground. The `code switch stays in this position until the end of the call and is unaffected by any further pulsing of relay H0. Relay 41 operated (a) disconnects the operator office from the operator oiiice trunk and connects it to the connector circuit of l Fig, 2A. If relay 94 is operated at this time its circuit will be open at the back contact and armature `3 of relay 41 whereupon relay 94 restores to normal. Relay'94 released releases relay 86 which in turn releases relay |0|.

When relay |20 operates it (a) disconnects the subscribers line from its line-circuit in the dial oiiice equipment |09 and connects it to the rightof -way connector circuit of Fig. 2A (b) connects the winding of relay |22 to theproper pick-up lead indicated by the broken line between ground and armature 2 of relay 20 and (c) connects the various ringing control leads for ringing the When the subscriber' |08 is on an individual line the operation otrelay |20 will operaterelay |22 immediately andringing will start immediately. Relay |23 is a ringing control relay and follows ringing code interruptions When the oiiice provides ringing current code directly relay |24 follows the ringing current code and in'turn operates relay |23. The operation of relay |23 disconnects the supervisory relay |25 from the lineuand connects ringing, current to the line and .at the same time'operates relay |26. Tripping is accomplished only during the silent interval.' When relay |23 releases at the end of eachringing interval relay |25 is connected to the line; relay |25 may kick up momentarily due to theline vdischarging but it is ineffective since the slow release relayl |26 holds the operating circuit of lgrelay |21 open until the Aconnectoris disconnected.

The subscribers answer is eiective only during the silent interval. When the subscriber answers Yduring such an interval relay |25 operates in turn operating relay |21. Relay |21 operated `(ci) .releases relay |22, (b) locks under control of relay 41` independently of relay |25 and (c) connectsthe front contact of relay |25 to relay 86 f yfor supervision.

are now operated: H0. H2, 41, |20, 86, |20,

'|0-I, |21 and |25. Relay |28 remains operated vas long as the connection to the operator oice trunk circuit is held. When the operator office trunk releases ground is removed from the sleeve releasing relay |28.I When rela-y |28 releases,

afseaaeo through the back contactjof relay y|28 A'to the sleeve conducto-r |29r as a busy condition. Relay .|28 is slow-releasing to permit the switch train to release before applying the-busy ground.

l Disconnection is under control ofthe operator.

When the operator disconnects relayI 0 releases causing operating relays and the code selector'to release, restoring the circuit to normal. What is claimed is: 1. In a communication system, a group of lines, machine switching meansl for interconnecting said lines, trunk circuits from said group to a distant switching point'for extending connections to and from the lines of saidhgroup, each said line being .designated for purposes of calling by a plural digit designation, certain of saidlines havingin addition a single digit designation and means controlled over one of saidtrunks responsive to the use of said single digit designations for establishing connections to said ycertain of said lines.

2. In a'cornmunication system, a group of lines,

tant switching point for extending connections to and from the lines of` said group, each said vline "being designated for purposesof callingby a plu- Vral digit designation, certain of said lines having in iii) additiona single Adigit designation, means responsive to the use of said single digit designations over one ofsaid trunks for establishing a preferred connection to the corresponding certain of said lines and means responsive to the establishment of said-'preferred connection for removing said line from the control of said machine switching-means. gY v 3. In a communication system, a group of lines, machine switching meansl for interconnecting said linesf'trunk circuits from said group to a vdistant switching point for extending connections to and 'from the lines of said group, each said line being designated for'purposes of calling by a plural digit designati'omrcertain of said lines having in addition a single digit designation,` an incoming selector controlled over said", trunks, and means for setting` said incoming selector "directly on said certain of said lines responsive to the use of said single digit designations.

4. In a communication system, a group o-f lines, machine switching means' Vfor interconnecting said lines, trunk circuits from said group' to a distant switching point for extendingconnections to and from the lines of said group, each said line being designated for purposesof calling by a plural digit designation, certain of said lines having in additi'ona single digit designation, an incoming selector controlled over said trunks,

means for establishing apreferred connection to said certain of said lines by controlling said incoming selector inV accordance `with saidV single digit designations and means responsive thereto for disconnecting said'selected line from lany connection with said machine switching means.

5. In a communicationl system, a group of lines, machine switching Y means for I interconnecting said lines, a trunkcircuit from said group to a distant switching pointV for extending connections to and from the lines of said` group, each said line being designated for purposes of calling bya plural digit designation, certain of Vsaid lines ,having in addition a single digit'ndesignation,

means in said trunk circuit responsive to control exercised over said trunk circuit from the distant end thereof in'accordance with said Vsingle digit asaaeeo designations for extending direct connections to j said' certain of said lines.

6. In a communication system, a group oflines, machine switching means for interconnecting said lines, a trunk circuit from said group to a Adistant switching point for extending connec-r tions to and from the lines of saidgroup, means to give emergency access to certain of said lines regardless of the busy condition thereof comprising a transfer relay individual to each one of `said lines, and an alternate pathleading'thereto, Said alternate path being accessible from said trunk circuit through the use of a single digit line number. v

7. In a communication system, a group of lines, machine switching means for interconnecting said lines, a trunk circuit from said groupto a.l f

distantswitching point forextending connections to and from the lines of said group, means acv cessible to said trunk and responsive to preferred single digit control for extending energ'ency'connections to certain of said lines regardless of the y busy condition thereof, means individual to said dition of saidftrunk distant switching point for extending connections I to and from the lines of said group, means controlled from the distant end of'said trunk for transferring said trunk from a path through said machine switching means to one of said lines to a path leading directly to oneof said lines.

9.. In a communication system, a, group of lines,

machine.' switching means for interconnecting vsaid lines,A a trunk circuit terminating in said machine switching means and leading to a distant point for extending connections to and from the 'lines ofv said group, means at the said distant zpoint to`dismiss any existing connection thereto and to establish 'a by-path direct connection to one of saidlines.

JOHN yBAUn/IFALBI.

preferred single digit 

